Automatic custody transfer system



April 30, 1963 L. M. HUBBY AUTOMATIC CUSTODY TRANSFER SYSTEM 5 Sheets-Sheet 1 Filed March 12, 1959 April 30, 1963 r M. HUBBY 3,0 7,3

AUTOMATIC cus'rooy TRANSFER SYSTEM Filed March 12, 1959 5 Sheets-Sheet 2 5 5 Efy g April 30, 1963 1.. M. HUBBY AUTOMATIC CUSTODY TRANSFER SYSTEM 5 Sheets-Sheet 3 Filed March 12, 1959 April 30, 1963 L. M. HUB-BY AUTOMATIC CUSTODY TRANSFER SYSTEM 5 Sheets-Sheet 4 L If;

Filed March 12, 1959 April 30, 1963 L. M. HUBBY AUTOMATIC CUSTODY TRANSFER SYSTEM 5 Sheets-Sheet 5 Filed March 12, 1959 United States Patent Filed Mar. 12, 1959, Ser. No. 798,979 14 Claims. (Cl. 73-223) This invention is concerned with liquid quantity measuring, in general. More specifically the invention is concerned with a system for automatic custody transfer. This is specifically applicable to petroleum liquids, e.g. crude oil.

Heretofore, the methods employed in custody transfer operations of oil from oil fields to a customer, have involved the use of personnel in manually measuring the quantity of oil as it is delivered, e.g. to a pipe line or other customer. Such manual operations were inefficient and expensive for various reasons, among which was the necessity for providing tank capacity sufficient to maintain a week-end supply of the oil being delivered in order that the personnel need not work full time over the weekend period, while the oil was still being produced. Furthermore, in measuring the quantity of oil being delivered, the measurements were subject to considerable errors .as the human factor entered in.

However, attempts to make the custody transfer operation automatic, have provided different and additional problems. Particularly, they have raised the question of reliability in remote areas where the supply of power required for motivating the automatic control is subject to interruption in its continuity.

Thus it is an object of this invention to provide an automatic custody transfer system, that is fully automatic in operation while being extremely reliable and foolproof in the results and measurements provided.

It is another object of this invention to provide a superior automatic custody transfer system which employs relatively simple and failure proof elements throughout.

Another object of the invention is to provide for animproved arrangement in an automatic custody transfer system, such that the transfer may be made in a fail-proof manner; whereby even though some of the elements controlling the automatic system were to fail, the measured quantity of fluid that was being delived, would not deviate outside of acceptable limits of error.

Still another object of the invention is to provide an automatic transfer system which will shut down in the event of failures, and hold the system at a given point of its operation to wait until the failure has been corrected. Thereafter, the system will recommence operating at the same point as when the failure occurred without any false indications, or spurious operations.

Yet another object of the invention is to provide an arrangement (in an automatic custody transfer system) that will count the number of dumps which are made of a measuring vessel, with .a fool-proof and failure-proof result. Thus, even though power failure should occur and be corrected, or various other difficulties should be encountered, the counting of the number of dumps of measured liquid will be absolutely accurate and no failure in this regard (including spurious counts) can occur.

Briefly, the invention concerns an automatic custody transfer system. The system comprises .a measuring tank, a motor actuated inlet and drain valve, and electric circuit means for controlling the actuation of said inlet and drain valve including a switch actuated by said inlet valve and a switch actuated by said drain valve. The said inlet and drain valve switches are each closed only when the corresponding valves are closed. Also, said circuit means includes said inlet and drain valve switches,

3,087,336 Patented Apr. 30, 1963 each in series with the control circuit of the other valve so that neither valve can be opened unless the other is closed.

Again briefly, the invention may be described as an improvement in an automatic custody transfer system. The improvement comprises means for delivering measured quantities of a liquid, wherein said liquid is measured by periodically filling and dumping a known volume receptacle. The invention comprises means for counting the number of dumps, said counting means comprising a rotary electric motor and a dump indicator driven by said motor.

Still another aspect of the invention may be briefly described as an improvement in an automatic custody transfer system that comprises means for delivering measured quantities of a liquid wherein said liquid is measured by periodically filling and dumping a known volume re ceptacle by gravity feed. The improvement comprises means for venting said receptacle to exhaust the gases therein as said liquid enters. Said venting means com'-' prises a passage extending above the maximum level of the source of said liquid. The said passage has a total volume from said maximum level to the full level of said receptacle, equal to less than a predetermined minimal percentage of the total volume of said receptacle, whereby the error in measurement of said liquid quantity is not unacceptable even under failure conditions.

The foregoing and other objects and benefits of the invention are set forth in greater detail below, and are illustrated in the drawings, in which:

FIG. 1 is a schematic showing of the principal elements in a system for automatic custody transfer of petroleum liquids;

FIG. 2 is an electrical circuit diagram illustrating the principal elements of the control system that is employed in connection with the elements illustrated in FIG. 1;

FIG. 3 is an enlarged plan view partially in cross section, showing the elements involved in a dump counter according to the invention;

FIG. 4 is an enlarged elevation view showing the housing in cross section and illustrating the same elements that are shown in FIG. 3;

FIG. 5 is a perspective view, further enlarged, showing the structure of the cam employed in the dump counter unit that is-illustrated in FIGS. 3 and 4;

FIG. 6 is a side elevation, somewhat schematic in nature showing a two measuring tank system for providing greater volume delivery of oil by alternate filling and dumping of the two tanks; and

FIG. 7 is an electrical circuit diagram illustrating the control system that is employed with the two tank arrangement according to FIG. 6.

Referring to FIG. 1, it is pointed out that there is illustrated in a schematic showing, an automatic custody transfer system that is employed with the delivery of" This represents one specific example of an crude oil. application of the invention; and it will be appreciated that there are other and different applications to which the invention is applicable. 1

In crude oil production and delivery, the oil coming from the well must be treated in various ways. Such treating is taken care of in connection with a tank 11' from 'which the oil flows over a connecting pipe 12, into a surge tank 13 where the oil undergoessettling and weathering. Clean oil is drawn off from an elevated point of the tank 13 via a pipe 14 that leads to a measuring tank, or receptacle 15. The quality of the oil is continuously monitored by a unit 19 that takes oil from the surge tank 13, just below the drain pipe 14'thereof, and circulates it through the unit 19 for such monitoring check. Also (as will appear more fully in connection with the circuit diagram of FIG. 2), the oil from the bottom of the surge tank 13 is periodically circulated back to the treating system for introduction into tank 11 again, by means of a return line 20 and a pump 21.

The monitoring unit 19 forms no part, per se, of the invention; and various types of monitoring units for accomplishing the desired check on the quality of the oil, may be employed.

Pipe 14 carries the oil from the surge tank 13 to a pump 24 that has a bypass-control valve 25, which is ordinarily kept open, for allowing gravity flow of the oil from surge tank 13 to the measuring, or dump tank 15. Pump 24 is employed for cold weather operation where the oil may be too viscous for allowing adequate gravity flow. When pump 24 is operated, there may be employed therewith a pair of float-controlled switches 26 and 27 to control the pump.

There is an inlet, or fill valve 30 that controls the introduction of oil to the measuring tank 15. Similarly there is a dump, or outlet valve 31 for controlling the dumping or emptying of the measuring tank 15 after it has been filled. The tank 15 is preferably constructed with a cone-shaped bottom for aiding in the drainage thereof in a complete manner, and the top also preferably has a slight slope to a high point, in order to aid in the venting of gas in the tank above the liquid as the liquid is introduced.

There is a chart recorder 34 that is permanently connected to the tank 15, and continuously records the temperature and the static pressure at the bottom of the tank. The pressure indication provides a means for checking the number of dumps which have been made during any recording period while the temperature in the tank gives an indication for determining the average temperature of the oil that was delivered for each dump of the tank.

Tank 15 is a predetermined volume, e.g. one hundred barrels, and has a liquid-level responsive unit 36- at the top thereof which is employed to control the closing of fill valve 30 as will be more fully described below in connection with the circuit diagram of FIG. 2.

There is a sump tank 37 that is connected to the downstream side of dump, or drain valve 31. There is a liquid level controlled unit 3 in the sump tank 37, which may be a float controlled switch. A pipe 41 connects the sump tank 37 with a pump 42 that delivers the oil via a valve 43 to the pipe line, or other customer.

Connected between the pump 42 and pipe line valve 43 there is a sampler unit 44 which acts to take a sample of the oil that is delivered each time the measuring tank 15 is dumped. These samples are usually comingled to provide a composite sample of all of the dumps over any given period of time.

Attached to the liquid level unit 36 there is a vent pipe 48 which acts to carry off the gas which is in the tank 15 above the liquid level thereof, as it is filled. It is pointed out that the vent pipe 48 extends vertically, to a height that is above the top of the surge tank 13 (which is acting as the source of the oil that is being measured in the tank 15). This is important in order to prevent the loss of oil, in the event that the controls in conjunction with the liquid level unit 36, should fail to cause a closing of the fill valve 30. In addition to this vertical height of the vent, the cross section area of the vent pipe 48 is made sufiiciently small so that the total volume within the vent pipe, up to the maximum level of oil in the surge tank 13, is less than a very small percentage of the measured volume of the measuring tank 15. Consequently, even in the event of a failure of the system which would allow the oil to fill above the full level of the tank 15, the total quantity of oil which could thus fill the tank would be within acceptable limits of error for a measured quantity. By way of an example, it is a simple matter to employ a vent pipe with a one hundred barrel tank, with the size of the vent pipe being such as to render the volume of oil which would be added, less than one tenth of a barrel of oil.

Of course, if the pump 24 is in use, vent pipe 48 should connect back to the top of the surge tank 13' to prevent possible loss of oil.

It will be appreciated that various types of liquid level responsive devices might be employed as the liquid level units 36 and 38, so long as the device may be adapted in a feasible way to provide for actuation of a switch so that a control system according to the invention may be employed. However, it is preferred to employ simple and reliable structure such as an arrangement employing a float-controlled switch as the level responsive element, in these units.

Referring to FIG. 2, the electrical control system will be described in connection with the circuit diagram there- The control system is largely electrical in nature, and the relationship of the electrical system thereof to the mechanical elements that are involved in the cycles of measuring the oil (by flowing it into the measuring tank 15 and dumping it therefrom) is indicated in FIG. 2 where the tank 15 and the fill valve 30, plus the dump valve 31 as well as the sump tank 37, are all shown. It will be appreciated that the electrical elements of the control system, are largely mounted in an instrument housing unit that is indicated by a dashed line 51. This unit has mounted therein an instrument panel that carries appropriate units of the control system elements. This panel is indicated as an enclosing dashed line box 52.

Electric power is fed to the system by means of a pair of input terminals 53 and 54 located on the instrument panel 52. Preferably, the electric power source is standard one hundred and fifteen volt A.C. current, that is generally available, although direct current may be employed of course.

The circuit showing is simplified by employing a grounded circuit. Thus the terminal 54 is shown directly connected to ground. It will be understood that the use of a common, or ground wire may be desirable to avoid circulating currents in the panel; but the circuit diagram is much clearer without showing such wire therein.

Some of the principal elements of the control circuit include a dump counter unit 55, which has as elements thereof a rotary type electric motor 56, and a revolution counter 57 for indicating the number of dumps of the measuring tank '15. Another element is a latching relay 60 which includes a main actuating coil 61 and a latch release coil 62, in addition to a mechanical latch 63 that is spring biased into the latching position so that in the absence of energization of the coil 62, when the main coil 61 is energized the relay will be actuated and latched to close a switch 66 and to open another switch 67 at the same time. It will be appreciated that the switches 66 and 67 are spring-biased, or otherwise arranged to open and close respectively, upon the release of the latch 63, whenever the main coil 61 is not energized.

'I he dump counter unit 55- has associated therewith, in addition to the revolution counter 57 that is driven by the motor 56, a double-pole double-throw switch structure that includes a switch 70 and a switch 7 1. This switch structure is actuated by a mechanical connection that is driven by the motor 56, and that is indicated by a dashed line in FIG. 2. The physical arrangement of this actuating structure, will be more fully described below in connection with FIGS. 3, 4 and 5.

Another principal element of the control system, is a float actuated switch 74 that is controlled by the full level of the liquid in measuring tank .15. Similarly, there is a float-controlled switch 75 that has the float for controlling it located in the sump tank 37 so that whenever the level of the liquid in sump tank 37 falls below a predetermined level, the switch 75 will be actuated from the upper to the lower position thereof, and will thus indicate the drained condition of the tank 15.

Two more principal elements of the electrical control system are a switch 78 that is located on or adja-' cent to the drain valve 31 in Such a manner that the switch 78 is only closed when the valve 3-1 is closed. Similarly, there is a switch 79 that is located on or adjacent to the fill valve 30. Also likewise, switch 79 is open whenever the valve 30 is open, and is closed only when the valve 30 is tight shut.

There is a time delay relay 82 that has connected to the output, or switch circuit thereof a motor starter 83 that acts to energize an electric motor 84 for driving the pump 42 that will deliver the oil from the measuring tank 15 to the customer. While the schematic symbol indicates a three phase motor for the motor 84, it will be understood that this might be a single phase motor, or any other feasible type, depending upon the load to be handled thereby. The same holds true for a similar motor 89, referred to below.

The total control system includes a recirculationtimer unit 87 that is continuously energized and acts to periodically start up the recirculating pump 21 (FIG.

1) in order to keep the level of unacceptable oil-from building up to too great an extent within the surge tank 13. It will be observed that the timer 87 controls the actuation of a motor starter 88 which controls energization of amotor 89 that in turn drives the pump 21.

'It is pointed out that there is an over-ride circuit that is under control of a relay 92 which is energized in accordance with the conditions as determined by the monitoring unit 19. In this manner, should the oil be-' come unacceptable, the relay 92 will be energized and that the oil is acceptable, there will be a closing of a switch 93 to the left (as is viewed in FIG. 2) so that the relay 92 will be energized and the over-ride circuit (just described above) will be opened. On the other hand when the BS & W of the oil gets too high (quality unacceptable), the unit 19 will allow switch 93 to be positioned to the right and thus the relay 92 will be deenergized and an alarm circuit will be closed. The

alarm circuit includes an alarm timer :94 that may be set of any desired time delay, after which it will ac- It will becbserved that there is an alarm-silencer push-buttontuate a switch 95 to energize an alarm 96.

switch 97 that is normally closed, but that may be manually opened to stopthe alarm when the trouble has been duly noted.

It is pointed out that the abbreviation BS & W

stands for basic sediment and water which are the qualities that are measured by the monitoring unit 19, and which must be kept to a-predetermined acceptably, low limit.

A continuously energized motor 99 is for driving the chart recorder 34 (FIG. '1).

Referring to FIGS. 3, 4 and 5 the details of the dump counter unit 55 will be described. The revolution counter 57 may be a standard device, and has an input shaft 102 that has mounted thereon, for positive revolution therewith, a cam '103 that has a fiat surface 104 on the periphery thereof. The double-pole doublethrow switch mentioned above (switches 70 and 71) is mounted in a housing 105, and is actuated-from one position to the other by means of a spring biased actua-- tor 106 which bears against the peripheral surface of' the cam .103.

The size of the arc subtended by the fiat surface 104' Directly coupled to the shaft 102 by a collar 109' there is anoutput shaft 110 of the motor 56. Motor 56 thus drives the counter 57 and the cam 103, whenever it is energized. It is pointed out that the motor 56 is a standard type of synchronous induction motor, and it has a coil':111- that is mounted on armature material 112 for carrying the electric flux into the vicinity of a gear-type rotor (not shown) which is employed in this type of induction motor.

Operation of Single Tank Measuring System The operation of the single tank system, that has been so far described, may be most easily understood in connection with the circuit diagram of FIG. 2. It is pointed.

out that all of the relays are shown in their deenergized positions.

Assuming that the measuring tank 15 is empty, a complete cycle beginning. with the filling of this tank by opening of the till valve 30, will now be described.

First of all, a system energized switch 117 will be closed, and the following energized circuit for commencing a fill cycle may be traced. Beginning at power source. terminal 53, the fill valve energization circuit may be traced over a wire 121 to the switch 117 and then viawires 122 and 123 to the cam actuated switch 70; Switch 70 will. be in the position illustrated, so that it then. directs the energized circuit via another wire 124 to the floatiactuated switch- 74.

Since the tank =15 is empty, float switch 74 will be in the. lower position. (as illustrated in FIG. 2) and the circuit may be continued via another wire 125 which leads to a junctionpoint 128. Here the energized circuit divides, and one branch travels over a wire 129 to one side of the latch release coil 62, the other side of which is. directly connected to ground as illustrated. Thus, the latch 63 is raised so that the switch contacts 66 and 67 of the relay 60 will be returned to the deenergized .positions (illustrated).

The other branch circuit may be followed continuing from junction point 128 over a wire 132 to a switch 133. Switch 133 is a so-called low-level-hold switch, which is manually actuated and is employed to stop the auto-- matic cycle: of the system with the tank empty. Therefore, during normal operation, switch 133 willlbe closed..

Thus the other'braneh circuit may be continued beyond switch 133 via another wire 134. to a normally open switch 135that is located on the BS & W relay 92'.

Switch 135 will be closed'ifthe relay 92 is energized. This will be. the. case .so long :as the monitored condition of the oil being delivered, is. of acceptable quality as indicated'by the BS & W unit 19 that is continuously monitoring: the oil. Unit 19 has the switch 93 as an' element thereof, and it isv actuated to the left' hand position (as viewed in FIG. 2 so long as the percentage of BS &*W is' below an acceptable limit;

Continuing to follow the other branch of the energized circuit, it continues from the closed switch 135. via an-' other wire 13-8 to the switch 78 that is located on the of switch 7-8, via a wire I139 to one side of'a-solenoid 140 the other side of which is connected directly to ground as illustrated.

Energization of the solenoid 140 acts to control the opening of valve 30 so as to allow oil to enter andfill the tank 15; which a this time has the drain valve 31 thereof, tight shut. It will be noted that the switch 78 on valve 31 acts to secure that the drain valve 31. will be closed before the fill valve 30 is actuated to its open position, since solenoid 140 cannot be energized until the drain valve 31 (and switch 78) is closed.

It will be understood that the motor actuated valves 30 and 31 may take 'various forms, and the structure thereof per se, forms no part of the invention. Thus, these motor actuated valves 30 and 31 could be solenoid operated with mechanical bias to the closed position, so that when the electrical solenoid is energized the bias is overcome and the valve is opened. However, it is preferred to employ a pneumatic diaphragm-actuated type of valve, that is biased to the closed position and opened under pneumatic pressure as applied to a diaphragm. The control of the supply of pneumatic pressure to open the valve is pilot-controlled, with the pilot having an electric solenoid for actuating same. Thus the solenoid 140 is a pilot-actuator that shifts a pneumatic pilot valve, for causing pneumatic control of the main valve 30 in order to open same. Furthermore, when the solenoid 140 is deenergized, the pilot valve will be returned to its original position so that the main valve 30 will again be closed.

While fill valve 30 remains open, the tank 15 will fill with oil. When it has reached the top, or rfull condition, it will cause the float-actuated switch 74 to be raised to the upper contact position. Therefore, it will open the above traced energized circuit, between wire 124 and 125 and transfer energization to a wire 144 that leads to switch 67 of the latching relay 60. The energized circuit that is thus deenergized includes latch coil 62 of the latching relay 60, as Well as the control solenoid 140 of the fill valve 30. Therefore the fill valve will close, and the latch on the .latching relay will be released.

At the same time, the newly energized circuit will energize motor 56. The circuit for accomplishing this may be traced from wire 144, via the switch 67 and a wire 145, to the cam actuated switch 71 which stands in the position illustrated, i.e. closed into contact with the circuit of wire 145. This then completes a circuit to energize the motor 56, via another wire 146 (between switch 71 and the motor), since the other side of the motor 56 is connected to ground, as illustrated. This will cause the motor 56 to run and drive its shaft (along with the cam 103) through about one-tenth of a revolution; after which the cam will cause actuation of the switch 71 to its other (or drain) position, so that the energizing circuit for motor 56, which was just traced, will be opened.

When the motor 56 is stopped by reason of the shifting of the switch 71, switch 70 is simultaneously switched to its other position (these two switches are both to- 'gether a double pole double throw switch actuated by the cam 103, as indicated above). The switch 70 thus shifts energization from the circuits traced above (when switches 70 and 71 were in the fill position) to a drain circuit that may be traced as follows.

From switch 70 an energized circuit extends via a wire 150 to the switch 79 on fill valve 30. Switch 79 will be closed so long as the fill valve 30 is tight shut.

Then the circuit may be continued beyond switch 79 (now closed) via a wire 151 to a junction point 152. Here the energized circuit divides, one branch going via a short wire '153 to one side of a solenoid 154 that controls the actuation of valve 31 to the open position thereof. Thus a draining of the measured quantity of oil from the tank 15 is begun, so long as the fill valve 30 was tight closed.

Here again, the solenoid 154 is preferably a pilot valve control solenoid such that the main valve 31 is actuated under control of such pilot valve, to be opened when the 154 is deenergized. However, the structure of the motorized valve 31 may take difierent forms in like manner as was described above in connection with fill valve 30.

The other branch energized circuit may be traced from junction point 152 to the switch 75 which will be raised to the upper position, i.e. to a contact 157, as soon as the sump tank 37 is filled enough to raise the float actuator of switch 75. Then the circuit may be continued via a wire 158 to one side of the time delay relay 82, the other side of which is connected to ground, as illustrated. The time delay relay 82 is a delayed closing, quick-opening type, and after the predetermined delay period will close its switch contacts .159 and so carry the energized circuit on via a wire 160 to a junction point 161.

At junction 161 the energized circuit divides again and one branch is closed via a wire 164 to one side of the coil 61 of latching relay 60. The other side of the coil 61 is connected directly to ground as illustrated. This will pull in the switches 66 and 67 of the relay 60 and latch them in the pulled-in position, since latching coil 62 is no longer energized and the latch 63 will be effec tive to hold them in their pulled-in position. Closing of switch 66 will not have any efifect at this time, even though the cam actuated switch 71 is standing in the drain position, for the reason that the switch 75 (float controlled in the sump tank 37) stands in its upper position by reason of the sump tank being full of oil as the measuring tank 15 is being drained.

The other energized branch circuit (beyond the junction point 161) may be traced via a wire 167 to one side of the energizing coil in the starter "83, the other side of which coil is connected to ground via another wire 168, as illustrated. This energized circuit therefore, actuates the starter 83 and thus energizes motor 84 which drives the pump 42 to deliver oil from the sump tank 37 via the pipe 41, to be received by the pipe line or other customer.

Circuit conditions will remain as last described above while the oil from tank 15 is draining, and until the measuring tank 15 is completely empty. After this the level of oil in the sump tank 37 will fall sufficiently to allow float switch 75 to be positioned to the lower position, i.e. as shown in the FIG. 2 illustration. This will deenergize the circuit that was traced including the time delay relay 82 and everything thereafter, and consequently the pump 42 will stop.

It will be observed that the circuit for energizing drain valve solenoid 154 of the drain valve 31, has not been disturbed at this stage in the cycle of events, s-6 that the drain valve 3-1 will remain open. Furthermore the switch 75 when it is changed to the lower position will now energize a dump count circuit, that may be traced via a wire 171 to the now closed switch 66 of the latching relay 60 (relay 60 remains latched because it had been cooked and not tripped again). Then the energized circuit continues on the other side of switch 66, via short wire 172 to the cam actuated switch 71 (now in drain position) and then via the wire 146 to one side of the motor 56 which will be energized once more.

Consequently the motor 56 is energized and runs to rotate its shaft and the cam 103 through the remaining nine-tenths of a revolution thereof. During this time the drain valve 31 will remain open, allowing the measuring tank 15 to complete draining into the sump tank 37. Also during this nine-tenths of a revolution of motor 56, it will actuate the revolution counter 57 to indicate a count, that is indicative of a dump of the measuring tank 15.

At the end of the revolution of the shaft of motor 56, the cam 103 will cause switches 70 and 71 to be repositioned back to the original or fill position, as they are shown in FIG. 2'. Then another cycle will be commenced if conditions are such as to warrant same.

It will be noted that when switch 70 is returned back to the original position, the energizing circuit for drain valve 3-1 will be opened so that the solenoid 154 will be deenergized, and valve 31 will close.

It is pointed out that, by reason of employing the type of dump counter unit 55 that is illustrated (which makes use of a rotary type electric motor 56) the system is rendered free from the possibility of creating spurious count indications when actual measuring dumps, or deliveries of the oil, have not been made. This will be clear when it is observed that if the power supply to the system (as connected at terminals 53 and 54) should fail at any time throughout the above described cycle of operations, the operation of the system will merely be arrested where it stands, and the dump counter 55 will not make a spurious dump count indication when the power is restored, such as would be the case were a spring biased, solenoid operated counter drive to be employed.

The control circuits for the auxiliary elements, that were described above, are clear and will be obvious to anyone skilled in the art. Consequently no detailed description of these circuits needs to be given. It may be briefly pointed out, however, in connection with the recirculation of the oil from the bottom of the surge tank 13, that it is periodically carried out under the control of the timer 87 and the over-ride circuit. The over-ride circuit will cause energization of the motor 85 to drive the pump 21, irrespective of the condition of the timer 87; because the over-ride circuit is connected in parallel with the energizing circuit of the timing unit 87, by means of the pair of contacts illustrated, that are carried by the BS & W relay 92.

Two-Tank System-FIGS. 6 and 7 In the event that an oil field system is sufliciently large that the allowable quantity of oil could not be delivered by a single tank automotive system in accordance with the above, because of the time consumed in each drain part of the cycle; the system according to this invention may be applied to two tanks, which are set up to operate alternately. Thus, while one tank is filling the other may be dumping, and vice versa. Such an arrangement is illustrated in FIG. 6 with the control circuits therefor shown in FIG. 7.

Referring to FIG. 6, it will be observed that there are two measuring tanks 175 and 176, each having their in-- dividual fill valves and drain valves in conjunction therewith. A fill valve 177 controls the inlet of oil to the measuring tank 175, while a drain valve 178 controls the outlet of oil therefrom. Similarly in connection with tank 176, there is a fill valve 181 and a drain valve 182.

For supplying the oil to fill the tanks, there is a common supply pipe 183. Similarly, there is a common sump tank 184 into which both of the tanks 175 and 176 drain. In the sump tank 184 there is a single float switch 187, and there is a baffle 188 to prevent a vortex above the outlet which might cause false actuation of the float switch 187.

Connected to the sump tank 184 there is an outlet pipe 189 that is connected to a valve 190 which controls the delivery of the oil to the customer.

At the top of each tank 175 and 176, there is a float switch housing 193 and 194 respectively. Connected above each of the float switch housings 193 and 194, there is a vent line 195 and 196 respectively.

Preferably, vent lines 195 and 196 extend vertically to a height above the maximum effective head of the source of oil that is connected to the inlet pipe 183. Furthermore the cross section area of these vent pipes 195 and 196 are in each case sufficiently small, so that the total volume of the vent passage which would be filled in the event that failure of the system should occur (so as to allow the oil to fill the measuring tank 175 or 176 and rise to a steady state height within the vent pipe) 10 is less than the permissible percentage of the total volume of each measuring tank so that the error would be sufficiently small to a be acceptable even under such failure conditions.

Referring to 'FIG. 7 it will be observed that the main elements of the two individual control systemsthat are included in the whole two tank system, are generally similar to those corresponding elements that were found in the single tank measuring system. However, some of the additional elements that are necessary in providing for the two tank system are an extra latching relay 200, for insuring that only one of the two tanks is being filled at the same time, and similarly another latching relay 201 that is arranged to provide for insuring that only one of the tanks is drained at a time.

There is a dump counter unit 204 for the tank and similarly there is another dump counter unit 205 for the tank 176. Each of these dump counter units 204 and 205, is substantially the same as the dump counter unit 55 (FIGS. 3, 4 and 5) that was described in considerable detail above. But an additional element is shown in FIG. 7, for the dump counters 204 and 205, which was not shown with the dump counter 55 of the single tank system for simplicity, although of course it wouldusually be employed there too. This element is a switch 206 for the dump counter 204, and likewise is a switch 207 for the dump counter 205. These switches 206 and 207 are in each case actuated mechanically by the associated dump counter, i.e. by the revolution counter in connection with each counter unit.

It will be appreciated that it is a simple matter to arrange the switches 206 and 207, in each case, to be actuated upon the rotation of a predetermined number of revolutions (or dumps) that have been counted by the counter in each case. In this manner the allowable quantity of oil, to be delivered over a given period of time, can be preset into the dump counter or dump counters of the system; and when the last dump of oil has been measured and delivered, the system will be cut ofl to stop any further delivery. Furthermore, as will appear, the arrangement with the two-tank system is such that the allowable will be set as a combined total of both dump counters 204 and 205. Thus if it should be an odd numberof dumps (of the capacity of one tank) one counter will be set for just under half of the allowable, while the other counter will be set for just over half, so that the total will be the allowable even though it is an odd number of single-tank-capacity dumps.

It is' pointed out that the dump counter unit 204 has the corresponding pair of cam actuated double-poledouble-throw switch elements that are to be found in the dump counter unit 55. These are a pair of switches 2 10 and 211. These two switches are actuated simultaneously by a motor 212, in the same manner as motor 56 actuated the corresponding switches of the dump counter unit 55. The dump counter unit 205 has corresponding elements including a switch 214, another switch 215 and a motor 216.

There is a pair of relays 220 and 221 that are each energized so long as the corresponding tank 175 01 176 respectively, is in service in the automobile delivery control system.

There is a single relay 222. (center of the circuit diagram) that corresponds to the relay 92 of the single tank system, and is actuated by a corresponding BS & W'

monitor 19.

The tank-175-side of the control system is shown on' the left hand side of FIG. 7 and has a latching relay 225, which, like a corresponding latching relay 226 for 11 relay 227 (left hand side) for the tank 175, and time delay relay 228 (right hand side) for the tank 176.

Operation of the Two-Tank System It will be appreciated by anyone skilled in the art, that the operation of the two tank system is substantially the same as the operation for a single tank arrangement with some additional complications in order to provide for the desired interlock that will prevent filling, or especially draining, of both of the two tanks at the same time.

In order to set forth fully the operation of the two tank system, a portion of the complete operating cycle may be described in detail as follows.

Assuming that the tank 175 (which will be designated for simplicity tank 1), has been filled and has commenced to drain; the fililng of tank 176 (valves F and D -tank 2) will begin in the following manner.

The fill" latching-relay 200, will have been latched into its energized position when tank 2 (175) began to drain, by reason of the energization of a coil 231 thereof. The circuit for this energization of coil 231 may be traced beginning at an input terminal 232 where the power source is supplied. Then the circuit continues via a power switch 233, a wire 234 and another wire 235, to an out-of-service switch 236 of the tank 175. From there the circuit continues via a wire 237 to the switch 206, which is now closed in accordance with the explanation given above.

After switch 206, the circuit continues via a wire 240 and a wire 241 to the switch 210', which is in the opposite position from that illustrated so that the circuit continues via another wire 242 to a wire 243 and then to a switch 244 of relay 220'. The circuit continues via the switch 244 (that is in the other position from that illustrated) to a wire 245 that leads to one side of the coil 231 of relay 200. The other side of the coil 231 is connected directly to ground as illustrated, so that the complete circuit is carried back to the power source via another input terminal 246, to which the power supply is connected and that is also connected to ground as illustrated.

It is pointed out that, as was the case in the single tank circuit diagram, so here all of the relays are illustrated in their deenergized position by way of a convenient convention in showing such circuits.

Closing of the normally open contacts of relay 200 (fill interlock relay) will complete a circuit for energizing the fill valve 181 (P of tank 176 to open same so that it (tank 2) may begin filling at this point. This energizing circuit may be traced as follows. Beginning at a common junction point 250 of the main supply circuit, the circuit may be traced via a wire 251 and a switch 252 that is now closed. Switch 252 is Similar to switch 236 on the other side of the circuit, and it is for taking tank 2 (176) out of service.

Continuing to trace the energizing circuit from switch 252, it goes on via wire 253 to now closed switch 207, then via wires 254, 255 and 256 to the switch 214. Then continuing on the other side of switch 214 the circuit includes wires 257, 258 and 259 to a switch 260 on the latching relay 200. From switch 260 the circuit continues via a wire 261 and a now closed switch 262, to a wire 263 that leads'to a manual low level hold switch 264. From switch 264 the circuit continues via a wire 26-8 to the float controlled switch 194 that is in the low position as illustrated, so that the circuit continues via another wire 269 to a switch 270 that is actuated to its closed position only when the fill valve 177 (F of tank 1 (175) is tight shut.

The circuit then continues via a wire 271 back to a switch 272 located on the drain valve 182 (D of tank 2 (176). Switch 272 is similar in nature to the switch 270', in that it is closed only when the drain valve 182 is tight shut.

Finally, the circuit continues via a wire 273, from switch 272, to one side of a valve-control solenoid 274, the other side of which is connected to ground as illustrated.

Solenoid 274 is the control element for actuating fill valve 181 (F to its open position. This actuating of valve 181 may be accomplished in various ways, as was described above in connection with the fill and drain valve structures of the single tank system. Thus, it is merely necessary to remember that the valve 181 is arranged so that when solenoid 274 is energized, the valve will be opened; while, when solenoid 274 is deenergized the valve will close.

Now, without tracing the detailed circuit connections, the remainder of the cycle of filling and draining the tank 176, may be set forth as follows. When the float switch 194 is actuated to its upper position by the liquid level having risen to the top of the tank 176, the switch will be positioned to the other contacts and consequently the circuit which was previously traced for energizing fill valve 181, will be opened and the valve 181 /will close.

Furthermore, a circuit will be closed by the switch 194 (in its upper position) which will be carried via the now closed contact of latching relay 226 up to the switch 215,

and thence to energize the motor 216. Motor 216 will.

now be energized and operate to rotate its shaftand the cam which actuates switches 214 and 215, so as to switch these contacts over to the drain position. This will open the fill position contacts which were occupied during the first part of this cycle, described in detail above.

Such operation of the motor 216 only rotates its shaft through about one tenth of a revolution, i.e. in the same manner as was described above in connection with the motor 56 of the dump counter unit 55 in the single tank system. Consequently the revolution counter is not actuated to indicate a dump at this point.

Next, the drain valve D (182) of tank 2 (176) will be opened if tank 1 has completed its drainage; and if its drain valve D has closed again. Thus, in tracing the energization circuit for the drain valve 182 of tank 176 we may begin with the switch 214, which will be now in the opposite position from that illustrated. Therefore it will thus close a circuit that may be traced to the upper contacts of the latching relay 201.

It is pointed out that the upper contacts of relay 20 1 will be closed. Furthermore, this is a cross interlock arrangement with tank 1 (175), in that should it (175) not have completed its drain cycle by this time, the latching relay 201 would still be latched in its energized position so that the upper contacts thereof would be open.

Since the upper contacts of latching relay 201 are closed, however, the circuit may be traced on down to a switch 280 on the fill valve 181 (F This. switch 280 makes sure that the valve 181 is closed, by reason of its association therewith. Therefore the circuits may then be continued over the illustrated wires to a similar switch 281 on the drain valve 178 (D of tank 1 (175), and then back to one side of a solenoid 282 that controls the opening of drain valve D (182).

Next, when tank 2 (176) has completed its drain; the float switch 187, in the sump tank 184, will fall and consequently the contacts of the switch 187 will take up the lower position and close a circuit for energizing a relay 285. Energization of the relay 285 pulls its contacts down, so that a circuit which had been previously closed and which carried energization to the pull-in, or energization coil of the latching relay 226; is now switched over so as to transfer this energizing circuit via the outer (now closed) contacts of the latching relay 226, up to the motor 216 via switch 215 of the dump counter 205, which is now in the drain position. This therefore, is the end of the drain cycle for tank 2 (176) and a dump will be counted by the dump counter unit 205 when the motor 216 is thus energized. Because, motor 216 will drive its shaft for the remaining nine tenths of a revolution, which thereafter resets the contacts of switches 214 and 215 back to the original position, as illustrated.

It will be observed that in both the two tank control system and in the one tank control system there may be employed signal lamps, as illustrated, for indicating various steps of the operation as it is carried out.

It will be observed thatwith the system provided by this invention, a relatively simple yet extremely reliable and fool proof, automatic system is provided whereby the measuring and delivery of a liquid may be carried out without any attention from a human operator. Duringtthe carrying out of such automatic operation the various elements of the system are so arranged that any failure of single elements of the system will merely cause the system to shut down and await repair of such element failure. Furthermore because. of the interlocking circuit arrangements, the delivery of oil as counted by the dump counter cannot be erroneously carried out, in excess of the single measuring tank quantity. In addition it is to be noted that the indication of the dump counter is such that it cannot provide spurious indications which do not actually indicate a measuring dump of oil that has been delivered. Such spurious indications would be had if the dump count indicator were actuated by a mere solenoid type of actuator, under certain conditions of.

power failure and restoration. This is an important feature of this invention for the reason that most lease transfer systems are located'in relatively remote areas where the'power is subject ot the failure at quite frequent intervals during electrical storms and the like.

While certain embodiments of the invention have been described in considerable detail in accordance with the applicable statutes, this is not to be taken as in any way limiting the invention but merely as being descriptive thereof.

What is .claimed as the invention is:

1. An automatic custody transfer system comprising a measuring tank, motor actuated inlet and drain valves, electric circuit means for controlling the actuation of said inlet and drain valves including a switch actuated by said inlet valve. and aswitch actuated by said drain valve, said inlet and drain valve switches each being closedonly when the corresponding valves are closed, said circuit means including said inlet and drain valve switches each in series with the control circuit of the other valve so that neither valve can be opened unless the other is closed.

2. An automatic custody transfer system comprising a measuring tank, motor actuated inlet and drain valves, electric circuitmeans for controlling the actuation of said inlet and drainvalves including a switch actuated by said inlet valve and a switch actuated by said drain valve, said inlet and drain valve switches each being closed only when the corresponding valves are closed, said circuit means including said inlet and drain valve switches each in series with the control circuit of the other valve so that neither valve can be opened unless the other is closed, said electric circuit means comprising means for continuously causing cyclic operation of filling and draining said tank including a switch controlled by the full level of fluid in said tank, a switch controlled by the drained condition of said tank, and dump count means for counting each dump of said tank after it has been drained.

3. An automatic custody transfer system comprising a measuring tank, motor actuated inlet and drain valves, electric circuit means for controlling the actuation of said inlet and drain valves including a switch actuated by said inlet valve and a switch actuated by said drain valve, said inlet and drain valve switches each being closed only when the corresponding valves are closed, said circuit means including said inlet ad drain valve switches each in series with the control circuit of the other valve so that neither valve can be opened unless the other is closed, said electric circuit means comprising means for continuously causing cyclic operation of filling and draining said tank including a switch controlled by the full level of fluid in said tank, a switch controlled by the drained condition of said tank, and pump count means for counting eachdump of said tank after it has been drained, said dump-count means comprising electrical means for actuating a dump indicator, said electrical means being continuously in motion when energized whereby no false counts will be indicated in the event of electric power failure and restoration.

4. An automatic custody transfer system comprising a measuring tank, motor actuated inlet anddrain valves, electric circuit means for controlling the actuation of said inlet and drain valves including a switch actuated by said inlet valve and a switch actuated by said drain valve, said inletand drain valve switches each being closed only when the corresponding valves are closed, said circuit means including said inlet and drain valve switches each in series with the control circuit of the other valve so that neither valve can be opened unless the other isclosed, said electric circuit means comprising means for continuously causing cyclic operation of filling and drain-' ing said tank including a switch controlled by the full level of fluid in said tank, a switch controlled by thedrained condition of said tank, and dump count means for counting each dump of said tank after it has been drained, said dump count means comprising a rotary electric motor, and a dump indicator driven by said motor.

5. An automatic custody transfer system comprising a measuring tank, motor actuated inlet and drain valves, electric circuit means for controlling the actuation of said inlet and drain valves including a switch actuated by said inlet valve and a switch actuated by said drain valve, said inlet and drain valve switches each being closed only when the corresponding valves are closed, said circuit means including said inlet and drain valve switches each in series with the control circuit of the other valve so that neither valve can be opened unless the other is closed, said electric circuit means comprising means for continuously causing cyclic operation of filling and draining said tank including a switch controlled by the full level of fluid in said tank, a switch controlled by the drained condition of said tank, and dump count means for counting each dump of said tank after it has been drained, said dump count means-comprising an induction type rotary electric motor, a dump indicator driven by said motor, and positive mechanical coupling means for connecting said motor to said indicator.

6. An automatic custody transfer system comprising a measuringtank, motor actuated inlet and drain valves, electric circuit means for controlling the actuation of said inlet and drain valves including a-switch actuated by said inlet valve and a switch actuated by said drain valve, said inlet and drain valve switches each being closed only when the corresponding valves are closed, said circuit means including said inlet and drain valve switches each in series with the control circuit of the other valve so that neither valve can be opened unless the other is closed, said electric circuit means comprising means for continuously causing cyclic operation of filling and draining said tank including a switch controlled by the full level of fluid in said tank, a switch controlled by the drained condition of said tank, and dump count means for counting each dump of said tank after it has been drained, said dump count means comprising a low speed synchronous induction type rotary electric motor, a dump indicator driven by said motor, and a direct coupling from the shaft of said motor to said indicator.

7. An automatic custody transfer system comprising a measuring tank, motor actuated inlet and drain valves, electric circuit means for controlling the actuation of said inlet and drain valves including a switch actuated by said inlet valve and a switch actuated by said drain valve, said inlet and drain valve switches each being closed only when the corresponding valves are closed, said circuit means including said inlet and drain valve switches each in series with the control circuit of the other valve so that neither valve can be opened unless the other is closed, said electric circuit means comprising means for continuously causing cyclic operation of filling and draining said tank including a switch controlled by the full level of fluid in said tank, a switch controlled by the drained condition of said tank, dump count means for counting each dump of said tank after it has been drained, and two position means in circuit with said full level switch and with said drained condition switch for shifting positions only after a change in the other of said full level and drained condition switches whereby a series of spurious dump counts will be avoided in the event that either of said last named switches should stick.

8. An automatic custody trans-fer system in accordance with claim 7 wherein said two position means comprises a latching relay.

9. An automatic custody transfer system comprising a measuring tank, motor actuated inlet and drain valves, means for controlling the actuation of said inlet and drain valves including first switch means responsive to the position of said inlet valve rendering said control mean-s inoperative to actuate said drain valve except when said inlet valve is in closed position and second switch means responsive to the position of said drain valve rendering said control means inoperative to actuate said inlet valve except when said drain valve is in closed position, said first and second switch means each in series with the control circuit of the other valve so that neither valve can be opened unless the other is closed.

10. An automatic custody transfer system according to claim 9 including counting means and motor means having positive mechanical coupling means for connecting said motor to said counting means for driving said counting means, said counting means being driven by said motor for counting each dump after said measuring tank has been substantially drained whereby no false counts will be indicated in the event of electric power failure.

11. An automatic custody transfer system according to claim 9 wherein said liquid is supplied to said measuring tank under a gravity head, comprising means for venting said measuring tank to exhaust gases therefrom as said liquid enters, said venting means comprising a conduit extending above the maximum level of the source of said liquid, said conduit having a total volume less than a predetermined minimal percentage of the total volume of said receptacle whereby the error in measurement of said liquid quantity is not unacceptable even under failure conditions.

12. In an automatic custody transfer system according to claim 11, said conduit having a total volume from said maximum level to the full level of said receptacle equal to less than one tenth of one percent of the total volume of said receptacle.

13. An automatic custody transfer system comprising a measuring tank having an inlet valve and a drain valve, mean-s for supplying liquid to said measuring tank wherein said liquid is measured by periodically filling and draining said measuring tank, electric circuit means including a rotary electric motor for controlling the actuation of said inlet and drain valves, first switch means responsive to the position of said inlet valve rendering said control means inoperative to actuate said drain valve except when said inlet valve is in closed position and second switch means responsive to the position of said drain valve rendering said control means inoperative to actuate said inlet valve except when said drain valve is in closed position, said first and second switch means each in series with the control circuit of the other valve so that neither valve can be opened unless the other is closed, said electric circuit means including means responsive to the high level of liquid in said tank and means responsive to the drained condition to said tank for continuously causing cyclic operation of filling and draining said tank.

14. An automatic custody transfer system according to claim 13 including counting means and motor means having positive mechanical coupling means for connecting said motor to said counting means for driving said counting means, said counting means being driven by said motor for counting each dump after said measuring tank has been substantially drained whereby no false counts will be indicated in the event of electric power failure.

References Cited in the file of this patent UNITED STATES PATENTS 1,696,512 White Dec. 25, 1928 2,436,235 Sunstein Feb. 17, 1948 2,773,556 Meyers et a1 Dec. 11, 1956 2,831,350 Banks et al. Apr. 22, 1958 2,872,817 Pitts Feb. 10, 1959 2,966,798 Smith Jan. 3, 1961 2,977,796 Pope et al. Apr. 4, 1961 OTHER REFERENCES An article entitled Automatic Custody Transfer in Texas in the Oil and Gas Journal, vol. 54, No. 48, July 30, 1956, pp. 122, 123. A copy is available in Div. 36. 

1. AN AUTOMATIC CUSTODY TRANSFER SYSTEM COMPRISING A MEASURING TANK, MOTOR ACTUATED INLET AND DRAIN VALVES, ELECTRIC CIRCUIT MEANS FOR CONTROLLING THE ACTUATION OF SAID INLET AND DRAIN VALVES INCLUDING A SWITCH ACTUATED BY SAID INLET VALVE AND A SWITCH ACTUATED BY SAID DRAIN VALVE, SAID INLET AND DRAIN VALVE SWITCHES EACH BEING CLOSED ONLY WHEN THE CORRESPONDING VALVES ARE CLOSED, SAID CIRCUIT MEANS INCLUDING SAID INLET AND DRAIN VALVE SWITCHES EACH IN SERIES WITH THE CONTROL CIRCUIT OF THE OTHER VALVE SO THAT NEITHER VALVE CAN BE OPENED UNLESS THE OTHER IS CLOSED. 